Slither On! (A Let It Go Parody)
by Alithea Korogane
Summary: What if that scene in Season 2 Episode 16...became a musical? Join Koro-sensei, or the former Shinigami, as he belt out a tune after his escape and Aguri's death, and before his first day in Class 3-E!


**_AN: Kon'nichiwa! I am back with a new fanfic, and I could say, it has been a long time since I had one._**

 _ **So this is an one-shot parody fanfic called "Slither On!", well it was a parody of the legendary Frozen song, "Let It Go"! The occasional change of lyrics to fit Koro-sensei...*coughs***_

 _ **This story happens between Aguri's escape to Koro-sensei's first teaching day in Class 3-E.**_

 _ **Spoilers on Season 2 Episode 16, as you know.**_

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 _ **DISCLAIMER: I don't own Assassination Classroom or Frozen. They belong to their respective owners.**_

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 ** _"Nurunurunuru." -_** tentacles speaking

 _"Nurunurunuru." -_ Shinigami/Koro-sensei's thoughts

 _"Nurnurunuru"_ \- lyrics

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The newly formed crescent moon was shining...illuminating the night skies with is soft pale moonlight.

The former God of Death sighed, walking around a huge forest. It was near the laboratory where he was contained and experimented for a year by one Yangisawa Kotaru.

The moon was shining brightly above him, even though it was not as it was before, considering the fact that the 70% of the moon was destroyed in a single bright explosion.

He looked at his hands, still having Yukimura Aguri's blood stained on it. His hands, now long and wriggly, clenched as his heart panged tightly when he remembers the events of a while ago.

He never dares to look at his new body. It was unrecognizable, he knew that he is now something that is not human. Something dangerous. Something deadly.

If you could ask the God of Death a year ago, he will say that he would be thrilled to have that immeasurable power that could destroy the whole planet, before shooting point blank at you in the head.

Now, he wouldn't be so sure if he ever wants it. This immeasurable power...a destructive force that needs to be stopped.

He walked around, taking the calm and peaceful view of the lush green forest. The moonlight was illuminating the path, and the animals looked fearfully of him. He winced slightly. Even the animals were afraid of him.

Suddenly, someone spoke into his mind. It was a voice, a voice that comforts and terrifies him at the same time. It was a nagging feeling, and he could hear it echoing unto his head.

The voice spoke to him,

 ** _"Don't be afraid, my master."_**

The former Shinigami was shocked.

"Who are you?" he shouted, looking around him. He saw nothing, but the trees and the crescent moon.

He could hear it laughing gently.

 ** _"I am your tentacles speaking to you."_**

"Eh?" Shinigami was confused. How can this be? Maybe the tentacles have gained sentimentiality or is he going crazy?

The tentacles understood his confusion. **_"Do not be afraid. I will not hurt you... In fact, my master, I could grant your greatest wish... The wish that your heart desires. The wish that will make you who you will be in the future. The wish that could change everything,"_** the tentacles replied.

The Shinigami was shocked. "My...my greatest wish?"

 ** _"Yes."_**

The Shinigami thought deeply. _My greatest wish..._

 _That my heart desires._

 _What could that be?_

With this power, he could rule the world.

With this power, he could take revenge on that Yanagisawa bastard...and his very own apprentice for betraying him.

With this power, he could destroy this evil world that makes his life miserable.

But the Shinigami, the former greatest assassin, would not think of it.

The image of Aguri came to his mind. He remembered her undying sacrifice for him by taking the shot of the tentacle mine that was meant for him...and her last dying wish.

 _Please teach them..._ _so they won't be in the dark..._

 _What splendid tentacles...With these...I know you are going to be a splendid teacher..._

He closed his now glowing red eyes, as he took a deep breath and started to walk using his newly gained tentacles, as a slithering noise was heard. The wind was blowing gently, and he could feel it touching his pale cheeks.

The crescent moon seems to illuminate his path, as if it was looking at him.

He started to sing melodiously, as the environment seems to go along with him.

 _"The moon glows bright on the mountain tonight,_

 _Not a person to be seen._ "

He suddenly remembers the cage he had been during his one year of captivity. The glass walls where he could see Aguri doing her work, the only barrier to their friendship...and love. The bed where he slept and experimented on. The white walls that surrounded him.

It was his castle, his kingdom, his prison.

 _"A prison full of isolation,_

 _And it looks like I'm the king."_

He walked through the forest, as he reaches unto a clearing. The grass were swaying because of the breeze.

He opened his eyes and frowned a little. As an assassin, he could feel his bloodlust swell up. His bloodlust that fuels his motivation to kill. Shinigami tried hard to quell that, but it seems to fail. He sighed in frustration. He could not help it.

He was an assassin, a natural-born killer.

 _"Bloodlust was growing on me like a swirling storm inside,_

 _Couldn't keep it in,_

 _Heaven knows I tried. "_

He sighed again, his tentacles made slithering noises as he shook his head. He remembers his dark past, his dark childhood...How he was trying to survive everyday in a world full of danger. How he was trying to hide his fear and regret every time he killed anyone.

How he tried to forget his hate towards his dark life.

" _Don't let them in,_

 _don't let them see_

 _Be the bad guy you always had to be!_ "

He walked towards the center of the clearing,where there is a small stream flowing. He looked at his hideous reflection and winced slightly.

He could see slithering white tentacles in his head, twitching and moving, and he could see his glowing red eyes.

What a monster he had been.

He tried to smile, that everything will be just fine.

He looked again in his reflection. Is this what he wanted to be in his remaining year? A dangerous creature?

" _Conceal, just smile,_

 _Just let it hide_."

He could feel the tentacles' presence in his mind, comforting him.

 ** _" You can be someone you wished to be..."_**

Shinigami paused. _I can be someone I wanted to be..._

He looked at his tentacled hand, and Aguri's image appears on his mind.

He gasped and smiled smugly, clenching his hand. His mind suddenly had a bright idea.

What if he could use his tentacles... for good?

It was a great idea...he will use this great power for the sake of Aguri.

He stomped his feet/tentacles with determination, as he closed his eyes. He will definitely use his powers for good...

For Aguri.

And for her students.

" _Well now it's time!_ "

He looked at his hand as his tentacles in his head moves with grace. He smiled slightly as he imagined himself using these tentacles for something good.

But first, he need to release his pent-up emotions.

Besides, in order to fully control his tentacles, he need to control his emotional stability.

He opened his eyes and tries to control his tentacles fully by trying to grab some fruits on the trees. It takes him a few mistakes and a few broken tree branches, but he did it.

" _Slither on! Slither on!_

 _Can't hold it back anymore!_ "

While he took a bite from an apple, he was thinking of the memories of a while ago. He had damaged the lab due to his rampage, and more importantly, he was now bruising one Yanagisawa Kotarou's ego.

He snickered. That bastard deserves it. He could remember that bastard screaming in pain when he was hit by a glass shard in his left eye.

Even though it was a terrible idea to go beserk on that lab, that causes the death of his only true friend and secret crush, something good has came from it.

" _Slither on! Slither on!_

 _Turn away, ruin them all!_ "

He threw the remains of the apple on his side, while he was looking at his reflection at the stream.

He knew that Yanagisawa would call someone from the government or from higher positions to warn them about him. Of course, he will coat the truth with lies and fallacies to manipulate those idiots, and few moments from now, the world leaders will eventually informed of his existence.

But he doesn't care.

Besides, he knew he wouldn't easily be injured by simple weapons, such as normal guns and knives, thanks to one of Yanagisawa's simple tricks when he gone rampage.

" _I don't care what they'll going to do,_

 _Let it slither on,_

 _The weapons don't kill me anyway._ "

He walked and looked around his surroundings, his tentacles in his head swaying.

He had remembered Aguri's sacrifice. She was his first real friend, who teaches him about compassion.

It was all his fault that he forgot to see Aguri and save her from that mine. That mine was intended for him, but Aguri had taken the blast for him.

" _It's sad to think that I had lost that one I loved,_ "

He remembered Aguri's dying words again. She told him to use his new abilities to teach and guide her students.

And he will follow her legacy, her passion in teaching... he may not be as good in teaching as Aguri, he may be not as kind and sweet as her, but he will do his best to fulfill her wishes in his own _slither_ _y_ way.

" _But I have to keep my promise,_

 _Her legacy continues on!_ "

He shook his head, and looked at his tentacled hands, clenching them.

It is time.

" _It's time to see what I can do,_

 _Time to test these tentacles that I have now._ "

His tentacles in his head was floating gracefully, as he twirled around. He smiled, controlling his tentacles to do his bidding.

" _To teach, to care, to guide them all,_

 _A best sensei!_ "

Suddenly, he made himself float, his tentacles started to be in its flying position. As it turns out, he can fly and move at high-hypersonic speeds...courtesy of what he heard on Yanagisawa when he was attacking the lab.

He smiled smugly, his eyes glimmered, as he started to take off, harsh winds starting to blow around where he was standing earlier.

He could feel the wind on his face as he flew at hypersonic speed. It was refreshing, he felt that he was now free, that he was already one with the wind and sky.

" _Slither on! Slither on!_

 _I can break the speed of sound!_

 _Slither on! Slither on!_

 _You will ever see me fly!_ "

The tentacles whispered,

 ** _"I think I knew what your greatest wish is. I could see it..."_**

Shinigami smiled confidently, as he was now flying around the town of Kunugigaoka in the city of Tokyo, where he will be staying for his remaining one year.

He could feel the tentacles' joy and contentment, as they wrapped their presence on his mind. He could feel the warmness on his body.

 ** _"Your wish...is my command."_**

" _Here I fly,_

 _No one will take me down!_

 _Let it slither on..."_

He could feel the tentacles changing him, making him into a whole new person. He stopped, but he was still floating mid-air. He could feel the pain of transforming, but he tried not to cry out in pain and continued to float through the air, closed his eyes, as he was singing with determination.

" _My power slithers through the air unto the ground!_

 _My wish is to be weak, to be kind and caring all around!_

 _The crescent moon's glowing like a bright orb in the sky!"_

As he was still transforming on mid-air, he eventually raised the tie that Aguri had given to him on his "birthday" and started to sew the crescent moon emblem on it at the speed of Mach 20.

The moonlight was glowing brightly at him, illuminating him. If someone who had seen that, it would be a spectacular sight.

" _I'm never going back,_

 _The past is in the past!"_

The pain was gone as it started. Shinigami opened his now beady eyes, taking the surroundings around him.

He could see the mountain that was owned by Kunugigaoka Academy, where Aguri had worked as a teacher. He had also seen an old building on the top of it, and he could guess that it was the Class 3-E Building, Aguri's advisory class.

Suddenly, the tentacles spoke silently to him, contented that he had granted his wish,

 ** _"Your wish is now granted..."_**

He looked at his hands. It was changed, his former five fingers now became two yellow tentacled fingers. It was yellow colored, and kind of slimy, as similar to a slug. He touched his face, but he could feel the roundness of his new face. It was now larger, and it seems that he has no nose structure. He could feel his semi-permanent grin, a reminder that a good teacher smiles at his students with love and appreciation, and encourage them to do their best.

Any beauty conscious person would treat it as a nightmare.

But Shinigami doesn't care. He wanted to fulfill his promise to Aguri, and this is his opportunity to fulfill it.

" _Slither on! Slither on!_

 _I will rise like the crescent moon!_ "

" _Slither on! Slither on!_

 _This cold killer is gone!_ "

He landed on the side of the mountain, where he had made his robes to wear. He grabbed some leaves and other stuff from nature, and made it into a spool of thread and a needle. He thought of the designs of the robes, and decides which is the best.

He eventually decided on an academic dress, to fit his new life. A black academic robe over a red on ,and a graduation cap with a gold tassel was perfect for his new job.

 _I will fulfill your promise, Aguri, I will not waste your great sacrifice for me. I will use my remaining time molding young minds of your students, and nuture them into the successful people they are destined to be._

The wind suddenly blew, as if they had agreed. The newly transformed teacher-to-be touched his crescent moon tie, and closed his now beady eyes.

" _Here I stand,_

 _On a thrilling night!_

 _Let it slither on!_ "

A bunch of shooting stars suddenly appeared on the night sky, probably moon chunks left from the explosion.

A mysterious sound was heard around Kunigigaoka, and the residents suddenly awakened, shivering slightly.

What's strange is that these 27 teenagers **(A/N: Including Itona and Karma. Ritsu is not included.)** heard a mysterious and strange laugh echoed in their minds.

What they did not know is that in that particular day after, their lives will turn upside-down and will change them...forever.

 _"The weapons don't kill me anyway._ "

Then the yellow octopus opened his glowing red eyes.

 ** _NURUFUFUFUFUFUFU~_**

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 ** _AN: I will offer you, the omake in this story! Scroll down!_**

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 ** _~~~OMAKE~~~_**

"Koro-sensei..."

"Koro-sensei..."

"KORO-SENSEI!"

Koro-sensei snapped his beady eyes open. " Nyuyayu?" he moaned groggily, as he rubbed his eyes with his tentacles.

He wiped his saliva dripping from his grinning mouth as turned around and focused his eyes at the ones who had woke him up.

It was Shiota Nagisa, Kayano Kaede and Yuuma Isogai.

But considering the fact that his mind was still foggy because he was just recently woke up, he could not recognize what happened the past year, or who are these people.

"Um...who are you and who is Koro-sensei?" he asked groggily.

The three teens just looked at their teacher like he had grown a second head.

"Haha, very funny, Sensei," Kaede muttered as she tried to swipe an anti-sensei, only to be stopped by Nagisa.

"Koro-sensei, we are so sorry we had to disturb your beauty sleep, but it is class already and Karasuma-sensei asked you to come now!" Isogai chided.

"Nyu?" The octopus teacher was confused. Yeah, still confused. "Class? But I don't know what you are talking about kids...I was just outside, singing my powerful song, after what I did with the moon and escaped..."

Kaede raised her eyebrow, while Isogai's and Nagisa's face got blank.

"Singing?" The three asked in unison.

"But Koro-sensei, the lab accident you were involved in and the moon explosion, apparently not directly your fault that it explode...was already happened 10 months ago." Nagisa explained, as he sweatdropped.

Koro-sensei was surprised. "Lab accident?! How do you know about-" he sputtered in panic, as his beady eyes widened.

"You just told us the truth of your past a month ago, remember?" Nagisa tried to emphasize.

"Yeah, you told us the truth, especially about my sister's death, which I regret trying to kill you..." Kaede said, feeling guilty.

Koro-sensei was still confused, "Sister? Who's your sister?"

Kaede, Nagisa and Isogai was now annoyed by their teacher's antics. Tic marks now appeared on their heads.

"Yukimura Aguri, of course, Sensei, who else?!"

Suddenly, as the three mentioned Aguri's name, like magic, Koro-sensei's true memories of the past flew through his now alert mind.

 _Him holding the huge necktie, Aguri's gift for him, as he flew and crashed in a mountain..._

 _Him staying in a cave, studying all Japan's textbooks while making his robes to use for teaching..._

 _The tentacles asking him what he wants to be..._

 _Wait a minute..._

Koro-sensei widened his beady eyes, as he realized...

There was no singing and dramatic flairs involved in that fateful memory!

He had been the Class 3-E homeroom teacher for ten freaking months!

Kaede is Aguri's little sister Akari!

And worse, the class knew his past as the Shinigami!

Koro-sensei was dreadedly stumped in his seat, sweat starting to form from his face. Of course, these three was Aguri's students, currently **HIS** students.

And it was embarrassing making a fool of himself in front of them. He was just thankful Karma or Nakamura isn't here, or hell breaks loose.

"Maybe we should stop you watching Frozen a million times yesterday..." Kaede muttered, facepalmed, while Nagisa and Isogai nodded.

Koro-sensei just covered his embarrased face with his tentacles, as the memory of him singing tone-deafly to Let It Go and watching Frozen until 4am came to his Mach 20 noggin.

He shouldn't have watching that before sleeping...

He shouldn't have.

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 ** _AN: And that wraps my story called "Slither On"!_**

 ** _*embarrased*_**

 ** _So what do you think, bad? good? Needs improvement?_**


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